The present invention relates to a programmable dynamic voltage control apparatus, and more particularly, to a programmable dynamic voltage control apparatus which is capable of dynamically controlling voltage conversion of an output unit using data set in programmable memories, when various pieces of information sensed by a variety of sensors mounted in a vehicle are converted into electrical signals and then transmitted.
Recently, a semiconductor device mounted in a vehicle may include various circuits such as a digital/analog (D/A) converter circuit and a current generator circuit, which are mounted on one chip. The D/A converter circuit is mounted as an interface circuit between a digital circuit and an analog circuit, and the improvement in precision for linearity of an output analog signal has been requested.
FIG. 1 is a circuit diagram of a conventional resistor string-type D/A converter circuit. The D/A converter circuit 11 includes a divider circuit 12 having a plurality of resistors R1 to R8 corresponding to a 3-bit digital signal D2 to D0, a plurality of switches SW1 to SW6, and a plurality of inverters 13 to 15.
In the D/A converter circuit 11 configured in such a manner, the resistors R1 to R8 are added according to the bit number (=3) of the digital signal D2 to D0, and coupled in series between a high voltage VDD and a low voltage VSS. The switches SW3 and SW4 are coupled in parallel to the resistors R2 and R3 at the high voltage VDD, respectively, the switches SW5 and SW6 are coupled in parallel to the resistors R6 and R7 at the low voltage VSS, respectively, the gates of the switches SW3 and SW6 are configured to receive an inverted signal of the digital signal D0 through the inverter 15, and the gates of the switches SW4 and SW5 are configured to receive an inverted signal of the digital signal D1 through the inverter 14.
Thus, the D/A converter circuit 11 turns on/off the switches SW3 to SW6 according to the lower 2-bit digital signals D1 and D0, equally divides a voltage difference between the high voltage VDD and the low voltage VSS, and generates an analog signal Aout having a voltage of [(VDD-VSS)×(n/16)+VSS] corresponding to the digital input signal D2 to D0.
However, since the conventional D/A converter does not have a resistance value of 0Ω when the respective switches SW3 to SW4 are turned on, the added resistors are coupled to the switches and coupling wirings are added therebetween. Thus, a divided voltage to which a voltage difference between the high voltage VDD and the low voltage VSS is equally divided cannot be obtained. This may reduce the precision of conversion from the digital signal D2 to D0 to the analog signal Aout.
In this connection, Korean Patent Laid-open Publication No. 10-2000-0076576 published on Dec. 26, 2000 and referred to as Patent Document 1 has disclosed a voltage generator circuit and a D/A converter circuit, which are capable of dividing a voltage difference between a high voltage and a low voltage, generating a divided voltage, and obtaining an output with high precision.
According to Patent Document 1, the D/A converter circuit includes a voltage generator circuit configured to generate a plurality of output voltages corresponding to the bit number of a low-bit digital signal and a selector circuit configured to select one of the output voltages based on an upper-bit digital signal and generate an analog signal. The voltage generator circuit includes a first impedance element coupled to a first terminal to which a first voltage is supplied, a second impedance element having the same impedance as the first impedance element and coupled to a second terminal to which a second voltage is supplied, a third impedance element coupled between the first and second impedance elements and having a predetermined impedance, a first current source coupled to a first node between the first and third impedance elements, and a second current source coupled to a second node between the second and third impedance elements. The first and second current sources supply first and second control currents having a correlation value to the first and second nodes, maintain a voltage difference between the first and second nodes, and change the potentials of the respective nodes to potentials corresponding to the first and second control currents. Thus, the D/A converter circuit may obtain an output signal with high precision.
Furthermore, Japanese Patent Laid-open Publication No. 63-202131 published on Aug. 22, 1988 and referred to as Patent Document 2 has disclosed an A/D converter which corrects and outputs a digital signal based on a driving voltage stored in a nonvolatile memory unit.
According to Patent Document 2, the A/D converter includes an A/D conversion unit configured to convert an analog signal to a digital signal, a nonvolatile memory unit configured to store a driving voltage which is applied to the A/D conversion unit so as to drive the A/D conversion unit, and a correction unit configured to correct a digital signal outputted from the A/D conversion unit based on the driving voltage stored in the nonvolatile memory unit and output the corrected digital signal. Thus, the A/D converter may correct the digital signal based on the driving voltage stored in the nonvolatile memory unit.
In the conventional converter circuits, however, the former converter has high precision, but cannot rapidly perform dynamic voltage control when the dynamic voltage control is required. Furthermore, in the case of the latter converter, a microprocessor may perform A/D conversion using a voltage programmed in EEPROM, but does not dynamically convert or control a signal of a sensor, transmitted from an output terminal. Thus, the converter cannot be applied to an electronic system for vehicle, which requires dynamic voltage conversion or control.
Patent Document 1: Korean Patent Laid-open Publication No. 10-2000-0076576 published on Dec. 26, 2000
Patent Document 2: Japanese Patent Laid-open Publication No. 63-202131 published on Aug. 22, 1988